Latitudinal sealing mechanism for bag-packaging machine and a bag packaging machine having the same

ABSTRACT

A latitudinal seal mechanism includes seal jaws  78 , fixed cams  75,  cam followers  76,  a pair of partial cams  88 , partial cam followers  78   a,  rotational shafts  80 , coupling members  79,  and shaft support portions. The seal jaws  78  are heated, and move circularly such that the seal jaws  78  abut on and move away from tubular film. The fixed cams  75  have shapes that correspond to locuses of movement of the seal jaws  78.  The cam followers  76  support the seal jaws  78,  and move along the fixed cams  75.  The rotational shafts  80  move the cam followers  76  relatively about rotational centers of the rotational shafts  80.  The coupling members  79  couple the rotational shafts  80  and the cam followers  76.  The shaft support portions rotatably support the rotational shafts  80.  The partial cams  88  have a shape that corresponds to a locus of movement of the pair of seal jaws  78  when the pair of seal jaws  78  holds the tubular packaging films. The partial cams  88  make the pair of seal jaws  78  press against each other with the partial cam followers  78   a  therebetween. The partial cam followers  78   a  are supported by the pair of seal jaws  78.  The partial cam followers  78   a  engage the corresponding partial cams  88  when the pair of seal jaws  78  holds the tubular packaging film therebetween.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of copending U.S. patentapplication Ser. No. 09/472,064 filed on Dec. 23, 1999.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates to a latitudinal sealing mechanism for usein a bag-packaging machine. More specifically, the present inventionrelates to a latitudinal seal mechanism for use in a bag-packagingmachine that fills articles to be packaged in a bag while packaging thebag by sealing tubular packaging material longitudinally andlatitudinally. The present invention also relates to such bag-packagingmachine.

B. Description of the Related Art

There has been a longitudinal bag-packaging machine that fills articlessuch as foods to be packaged in a bag while manufacturing and packagingthe bag.

For instance, a longitudinal pillow packaging machine forms a packagingmaterial which is a sheet-shaped film into tubular shape by using aformer and a tube. Longitudinal seal means (heat sealing) sealslongitudinal edges of the tubular packaging materials that are placedone on top of another, thereby making bags. The pillow packaging machinefills articles to be packaged into the tubular packaging materialsthrough the tube. Latitudinal sealing mechanism below the tube seals theupper portion of a bag and the bottom portion of an following bag. Thenthe pillow packaging machine cuts the middle of the latitudinally sealedportion. In such pillow packaging machine, operations of making a bagand filling articles in the bag occur in a continuous manner.

An example of such bag packaging machine is disclosed in JapaneseLaid-Open Patent Application 10-86910. In the packaging machinedisclosed therein, the tubular packaging material is sealedlatitudinally by heating and pressing a pair of seal portions calledseal jaws against each other, with the pair of seal jaws opposing eachother across the conveyance path of the tubular packaging material. In astructure where the seal jaws simply repeat linear back and forthmovements, the packaging material is sealed only at a point (a line).Therefore, conveyance of the packaging material has to be stopped whilethe packaging material is being sealed in this structure. To avoid thisproblem, each seal jaw is controlled by two kinds of motors, such thateach seal jaw moves drawing a locus that is in the shape of letter D. Inthis way, enough sealing time is secured while conveying the tubularpackaging material continuously, by having the seal jaws follow thetubular packaging material. Motors used in this bag packaging machinefor controlling each sealing jaw include, a rotational motor forrotating each seal jaw, and a horizontal motor for moving each seal jawhorizontally back and forth.

Some of such mechanisms utilize a cam having a groove formed thereon, soas to engage inner and outer sides of a cam follower. U.S. Pat. No.5,031,386 discloses one of such mechanisms. In this mechanism, a camfollower that supports a seal jaw engages a cam having a groove that isformed in the shape of the letter D. The cam follower and the seal jaware supported by an end of a drive member fixed to a shaft. As the shaftrotates, the cam follower and the seal jaw move along the groove on thecam. In this manner, the seal jaw moves drawing a locus in the shape ofletter D.

Problem to be Solved by the Invention

Although the aforementioned mechanism allows the seal jaw to movedrawing a locus in the shape of letter D, the seal jaw and the camfollower need to be able to slide against the drive member, since theseal jaw moves drawing a locus in the letter of D instead of a circlewhile the drive member rotates.

However, it is structurally difficult to configure a sliding mechanismhaving bearings in the portion where sliding needs to occur.Consequently, the seal jaw and the cam follower have to slide againstthe drive member by contacting and slipping against the drive member.Furthermore, if multiple cam followers are coupled to the cam toincrease the processing speed of the bag packaging machine, themechanism is subject to even more strict space constraint. Also, as theprocessing speed of the bag packaging machine increases, theslip-sliding by the cam follower and the seal jaw against the drivemember may lead to a durability problem of the latitudinal sealingmechanism.

Further, packaging materials are becoming thinner recently. Accordingly,more pressure is required to seal the packaging material. This causes agreater reactionary force in the structure that supports each seal jaw.Especially in the structure disclosed in the aforementionedapplications, reactionary force occurs in the horizontal motor thatmoves each seal jaw horizontally back and forth. Consequently, thehorizontal motor has to be able to generate a torque that is largeenough to be able to oppose the reactionary force. In other words, thehorizontal motor is required of extra functions that would not benecessary if the horizontal motor were simply moving seal jawshorizontally. Also, the rotational motor has to rotate each seal jaw (ina downward direction) pushing the seal jaw against the reactionary forceapplied to each seal jaw. Therefore, the rotational motor also needs tobe able to generate torque that is comparable to the torque of thehorizontal motor.

In the structure where two kinds of motors rotate each seal jaw so as todraw a locus in the shape of letter D and thereby generate sealingpressure, the magnitude of sealing pressure can be easily adjusted byadjusting the horizontal motor. On the other hand, such structurerequires a high-powered motor that can generate torque comparable withthe sealing pressure, which leads to a higher cost of the bag packagingmachine.

In view of the above, there exists a need for an improved latitudinalseal mechanism for a bag packaging machine which overcomes the abovementioned problems in the prior art. This invention addresses this needin the prior art as well as other needs, which will become apparent tothose skilled in the art from this disclosure.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a latitudinal sealmechanism for use in a bag packaging machine that utilizes a cam, withthe latitudinal seal mechanism allowing a seal portion to move drawing alocus in a shape other than a near circle having the shape of the letterD, without utilizing a structure in which the cam follower and the sealportion (seal jaw) slide against a coupling member (drive member) fixedto a rotational shaft (shaft).

In accordance with one aspect of the present invention, there is alatitudinal seal mechanism for use in a bag packaging mechanism thatfills articles to be packaged while sealing a tubular packaging materialin longitudinal and latitudinal directions. The latitudinal sealingmechanism includes a seal portion, a fixed cam, a cam follower, arotational shaft, a coupling member, and a shaft support portion. Theseal portion is adapted to be heated and move circularly, such that theseal portion abuts on and moves away from the tubular packagingmaterial. The fixed cam has a shape that corresponds to a locus of themovement of the seal portion. The cam follower supports the seal portionand is adapted to move along the fixed cam. The rotational shaftrelatively moves the cam follower circularly about a rotational centerof the rotational shaft. The coupling member couples the rotationalshaft and the cam follower. The shaft support portion supports therotational shaft such that the rotational shaft can move in a directionthat crosses with a direction of an axial core of the rotational shaft.

The latitudinal seal mechanism moves the heated seal portion circularly,such that the seal portion seals the tubular packaging material by heatwhen the seal portion abuts on the tubular packaging material. The fixedcam has a shape that corresponds to the locus of the movement of theseal portion such that sealing conditions such as sealing time aresatisfied. The sealing portion is supported by the cam follower whichmoves along the fixed cam. The cam follower moves drawing apredetermined locus, thereby sealing the tubular packaging material.

The cam follower is coupled to the rotational shaft via the couplingmember. If the rotational shaft is fixed, the cam follower cannot movebut circularly. Therefore, in the latitudinal seal mechanism of thepresent invention, the shaft support portion supports the rotationalshaft such that the rotational shaft can move in a direction thatcrosses with the direction of the axial core (direction of length), forinstance in a perpendicular direction. In other words, in a conventionallatitudinal seal mechanism, the cam follower and the coupling member hadto slide against each other to allow the cam follower to move in anon-circular manner along the fixed cam. On the other hand, in thelatitudinal seal mechanism of the present invention, the rotationalshaft moves relative to the fixed cam, unlike the conventionalrotational shaft which is fixed to the fixed cam. When the rotationalshaft is movably supported, there is relatively more flexibility as towhere the shaft support portion should be disposed. Also, since there islarger space in which the shaft support portion can be disposed, theshaft support portion can include a slide mechanism having rollers, or apendulum-type support mechanism.

Therefore, the present invention eliminates conventional structure wherethe coupling member fixed to the rotational shaft slides against the camfollower and the seal portion. In this way, the present inventionprovides a more durable, desirable structure that can make the sealportion move drawing a locus other than a circle, such as one in theshape of letter D.

In accordance with another aspect of the present invention a latitudinalseal mechanism is adapted for use in a bag packaging mechanism thatfills articles to be packaged while sealing a tubular packaging materialin longitudinal and latitudinal directions. The latitudinal sealingmechanism includes a pair of seal portions, fixed cams, cam followers,rotational shafts, coupling members, and shaft support portions. Thepair of seal portions is adapted to be heated and move circularly, suchthat the seal portions hold the tubular packaging material therebetween.The fixed cams have shapes that correspond to a locus of the movement ofeach of the seal portions. The cam followers each support the sealportion, and are adapted to move along the fixed cams. The rotationalshafts relatively move the cam followers circularly about rotationalcenters of the rotational shafts. The coupling members couple therotational shafts and the cam followers. The shaft support portionssupport the rotational shafts such that the rotational shafts can movein a direction that crosses with direction of the axial core of therotational shaft.

In this latitudinal seal mechanism, the heated pair of seal portionsmoves circularly, and closes the packaging material by heat by holdingthe tubular packaging material therebetween. The latitudinal sealmechanism utilizes fixed cams having shapes that correspond to thelocuses of the movement of the seal portions, such that the sealingconditions such as sealing time are satisfied. Each seal portion issupported by the cam follower that moves along the corresponding fixedcam. The seal portions move drawing predetermined locuses, therebysealing the tubular packaging material.

The cam followers are coupled to the rotational shafts via the couplingmembers. If the rotational shafts are fixed, the cam followers cannotmove but circularly. Therefore, in the latitudinal seal mechanism of thepresent invention, the shaft support portion supports the rotationalshafts such that the rotational shafts can move in directions that crosswith the directions of the axial cores, for instance in a perpendiculardirection. In other words, in a conventional latitudinal seal mechanism,the cam followers and the coupling members had to slide against eachother to allow the cam followers move in a non-circular manner. On theother hand, in the latitudinal seal mechanism of the present invention,the rotational shafts move relative to the fixed cams, unlike theconventional rotational shafts which are fixed to the fixed cams.Therefore, when the rotational shafts are movably supported against thefixed cams, there is relatively more flexibility as to where the shaftsupport portions should be disposed. Also, since there is larger spacein which the shaft support portions can be disposed, the shaft supportportions can include a slide mechanism having rollers, or apendulum-type support mechanism.

Therefore, the present invention eliminates conventional structure wherethe coupling members fixed to the rotational shafts slide against thecam followers and the seal portions. The present invention provides amore durable, desirable structure that can make the seal portion movedrawing a locus other than a circle, such as one in the shape of letterD.

Preferably, in the latitudinal seal mechanism, at least two of the camfollowers are disposed for each fixed cam. First and second camfollowers, out of all the cam followers, are disposed on opposite sidesof the rotational shaft with the rotational shaft therebetween. Thefirst and second cam followers are supported by ends of the couplingmember, with a middle portion of the coupling member being fixed to therotational shaft.

Since a plurality of cam followers is disposed for each fixed cam,sealing can be conducted multiple times per one rotation of therotational shaft. Consequently, the bag packaging machine will be moreeffective (speedy).

Also, in this embodiment, the first and second cam followers aredisposed so as to hold the rotational shaft therebetween. Then, thefirst and second cam followers are coupled by the coupling member.Therefore, the cam followers move along the fixed cams even when thefixed cam is a plate cam that engages only an inner side of the camfollower, instead of a groove cam having a groove that couples bothinner and outer sides of the cam follower. In other words, the camfollowers do not disengage the fixed cams, even when the fixed cam is aplate cam. By allowing the rotational shaft to move relative to thefixed cam and couple the first and second cam followers to therotational shaft via the coupling member, the fixed cam can use a platecam which has a simpler structure than a groove cam.

Preferably, in the latitudinal seal mechanism, the fixed cams have suchshapes that make the pair of seal portions move drawing locuses thathave approximately the shapes of letter D and inverted letter D.

Since the pair of seal portion moves drawing the locuses that haveapproximately the shapes of letter D and inverted letter D, the sealportions can hold the tubular packaging material therebetween while theymove approximately linearly. Therefore, the pair of seal portions canseal the packaging material for a predetermined sealing time even whilethe tubular packaging material is being conveyed.

Preferably, in the latitudinal seal mechanism, the rotational shaftsrepeat stopping and linear back and forth movement as they rotate, dueto movement of the cam followers coupled to the fixed cams.

When the rotational shafts are supported by the shaft support portionsso as to allow the rotational shafts to slide linearly, the rotationalshafts repeat stopping and linear back and forth movement, as the sealportions move drawing locuses other than a circle such as ones in theshapes of letter D.

Preferably, the rotational shafts repeat stopping and arc-shaped backand forth movement as they rotate, due to movement of the cam followerscoupled to the fixed cams.

When the rotational shafts are supported by the shaft support portionsso as to allow the rotational shafts to slide drawing an arc, therotational shafts repeat stopping and arc-shaped back and forthmovement, as the seal portions move drawing locuses other than a circlesuch as ones in the shapes of letter D.

Preferably, the rotational shafts are rotatably supported by bearings.The shaft support portions support the bearings such that the bearingscan move in a direction that cross with the direction of the axial coreof the rotational shaft.

The bearings for rotatably supporting the rotational shafts are movablysupported by the shaft support portions. Therefore, the shaft supportportion can utilize a support mechanism in which the bearings slidelinearly with little friction, or in which the bearings support therotational shaft via an arm such that the bearing can move in the shapeof an arc.

Preferably, each of the fixed cams includes an elongated bore formedthereon. The rotational shafts pass through the elongated bores of thefixed cams.

The fixed cams include an elongated bore, which is an elongate opening.Therefore, the rotational shafts that move relative to the fixed camscan cross with the fixed cams. Consequently, there is more flexibilityas to where to dispose the shaft support portions that support thebearing. There is also larger space in which the shaft support portioncan be disposed. Therefore, the shaft support portion can utilize adurable mechanism such as a slide mechanism having rollers or pendulumtype support mechanism.

In accordance with still another aspect of the present invention thereis a latitudinal seal mechanism for use in a bag packaging mechanismthat fills articles to be packaged while sealing a tubular packagingmaterial in longitudinal and latitudinal directions. The latitudinalsealing mechanism includes a seal portion, a fixed cam, a cam follower,a rotational shaft, and a coupling member. The seal portion is adaptedto be heated and move circularly, such that the seal portion abuts onand moves away from the tubular packaging material. The fixed cam has ashape that corresponds to a locus of the movement of the seal portion.The cam follower supports the seal portion and is adapted to move alongthe fixed cam. The rotational shaft relatively moves the cam followercircularly about a rotational center of the rotational shaft. Thecoupling member couples the rotational shaft and the cam follower. Therotational shaft is adapted to move in a direction that crosses with adirection of its axial core due to movement of the seal portion and camfollower.

In the latitudinal seal mechanism, the heated seal portion movescircularly, and seals the tubular packaging material by heat when theseal portion abuts thereon. The shape of the fixed cam corresponds tothe shape of the locus of the seal portion, such that sealing conditionssuch as sealing time are satisfied. The seal portion is supported by thecam follower that moves along the fixed cam. The seal portions movedrawing predetermined locus, thereby sealing the tubular packagingmaterial.

The cam follower is coupled to the rotational shaft via the couplingmember. If the rotational shaft is fixed, the cam follower cannot movebut circularly. Therefore, in the latitudinal seal mechanism of thepresent invention, the rotational shaft is supported such that therotational shaft can move relative to the fixed cam in a direction thatcrosses with the direction of the axial core, for instance in adirection perpendicular to the direction of the axial core. In otherwords, in a conventional latitudinal seal mechanism, the cam followerand the coupling member had to slide against each other to allow the camfollower to move in a non-circular manner. On the other hand, in thelatitudinal seal mechanism of the present invention, the rotationalshaft moves relative to the fixed cam, unlike the conventionalrotational shaft which is fixed to the fixed cam. Therefore, when therotational shaft is movably supported against the fixed cam, there ismore flexibility as to where the shaft support portion should bedisposed. Also, since there is larger space in which the shaft supportportion can be disposed, the shaft support portion can include a slidemechanism having rollers or a pendulum-type support mechanism.

Therefore, the present invention eliminates conventional structure wherethe coupling member fixed to the rotational shaft slides against the camfollower and the seal portion. The present invention provides a moredurable, desirable structure that can make the seal portion move drawinga locus other than a circle, such as one in the shape of letter D.

In still another aspect of the present invention there is a bagpackaging mechanism that fills articles to be packaged while sealing atubular packaging material in longitudinal and latitudinal directions.The bag packaging mechanism includes forming means, a packaging materialconveyance mechanism, a longitudinal seal mechanism, and a latitudinalseal mechanism. The forming means forms a sheet-shaped packagingmaterial supplied thereto in tubular shape while receiving the articlesto be packaged. The packaging material conveyance mechanism conveys thetubular packaging material in a downward direction. The longitudinalseal mechanism seals in a longitudinal direction overlapping portions ofthe tubular packaging material conveyed thereto. The latitudinal sealmechanism is a latitudinal seal mechanism described above, and seals ina latitudinal direction portions of the tubular packaging materialconveyed thereto with a predetermined distance therebetween.

In still yet another aspect of the present invention there is alatitudinal seal mechanism of a bag packaging machine, where thehorizontal motor does not oppose the sealing pressure and therefore canbe reduced in size. Alternatively, the latitudinal seal mechanism doesnot utilize a horizontal motor but generates sealing pressure, in whichthe sealing pressure can be configured.

In accordance with still another aspect of the present invention thereis a latitudinal seal mechanism for use in a bag packaging mechanismthat fills articles to be packaged while sealing a tubular packagingmaterial in longitudinal and latitudinal directions. The latitudinalsealing mechanism comprises a pair of seal portions, a pair of partialcams, and partial cam followers. The pair of seal portions is adapted tobe heated and move circularly, such that the seal portions hold thetubular packaging material therebetween. The pair of partial cams has ashape that corresponds to a locus that the pair of seal portions drawswhen the pair of seal portions holds the tubular packaging materialtherebetween. The pair of fixed cams makes the pair of seal portionspress against each other. Each of the partial cam followers is supportedby the pair of seal portions. The partial cam followers engagecorresponding partial cams when the pair of seal portions holds thetubular packaging material therebetween.

This latitudinal seal mechanism moves the heated pair of seal portionscircularly, such that the seal portions crimp by heat (seal) the tubularpackaging material by holding the tubular packaging materialtherebetween. This latitudinal seal mechanism also includes a pair ofpartial cams and partial cam followers for securing sealing pressure.Each of the partial cam followers engages the partial cam.

The partial cam follower is supported by the seal portion. As each ofthe seal portions moves circularly, the partial cam followers engage thepartial cams shortly before the pair of seal portions holds the tubularmaterial, while the pair of seal portions holds the tubular materialtherebetween, and shortly thereafter. The pair of seal portions crimpsthe tubular packaging material by heat through pressure applied from thepartial cams via the partial cam followers, while the partial camfollowers engage the partial cams.

Here, the reactionary force that occurs in the seal portions during thesealing is applied to the partial cams via the partial cam followers.Therefore, by fixedly disposing the partial cams and/or by allowing thepartial cams to generate force that opposes the reactionary force of theseal portions, the driving means that move the seal portions circularlyare not affected by the reactionary force of the seal portions.

Preferably, the latitudinal seal mechanism should comprise pressuremeans for applying pressure to the partial cams such that the pair ofseal portions press against each other when the pair of seal portionsholds the tubular packaging material therebetween.

The reactionary force of the seal portions applied to the partial camsvia the partial cam followers is at equilibrium with the pressureapplied from the pressure means to the partial cams. Therefore, whilethe pair of seal portions holds the tubular packaging materialtherebetween, the seal portions are pressed against each other. In thismanner, the tubular packaging material can be sealed securely with apredetermined pressure.

By allowing the pair of seal portions to separate from each other whilethe pressure means does not apply pressure to the partial cams, pressurecan be applied by the pressure means to the partial cams only when thetubular packaging material needs to be sealed. When the tubularpackaging material does not need to be sealed, for instance when thequality of articles to be packaged is not guaranteed, the pressure meanscan be configured not to apply pressure to the partial cams. In thismanner, substandard articles can be thrown away before they arepackaged.

Preferably, the latitudinal seal mechanism should comprise pressureadjustment means for adjusting the magnitude of pressure that thepressure means applies to the partial cams.

By adjusting the magnitude of pressure that the pressure means appliesto the partial cams, the pressure by which the seal portions pressagainst each other, in other words the sealing pressure can be adjusted.In this manner, besides that the sealing pressure can be secured by thepartial cams and the partial cam followers, the sealing pressure canalso be adjusted by the pressure adjustment means.

Preferably, in the latitudinal seal mechanism, the pair of partial camsis connected via a link mechanism. The pressure means applies force to aportion of the link mechanism in a direction that crosses with adirection in which the pair of seal portions is pressed against eachother.

Here, the link mechanism connects the partial cams. The sealing pressureis generated by applying pressure to a portion of the link mechanism.Therefore, only one pressure means generates sealing pressure forpartial cams, instead of having to dispose pressure means for eachpartial cam.

In this mechanism, the pressure means applies pressure not in adirection in which the pair of seal portions is pressed against eachother (sealing pressure direction), but in a direction that crosses withthe sealing pressure direction). In this manner, greater sealingpressure can be generated with smaller pressure.

Preferably, in the latitudinal seal mechanism, the pair of partial camincludes on each opposing surface an entrance surface, a pressuresurface, and an exit surface. The pressure surface is formed immediatelybelow the entrance surface. The exit surface is formed immediately belowthe pressure surface. The pair of seal portions receives no pressureapplied thereto while the partial cam followers engage the entrancesurfaces. The pair of seal portions is pressed against each other whilethe partial cam followers engage the pressure surfaces. The pair of sealportions receives no pressure applied thereto while the partial camfollowers engage the exit surfaces.

As the partial cam followers supported by the seal portions that movecircularly approach the partial cams, the partial cam followers firstcontact and engage the entrance surfaces. At this point, the pair ofseal portions is apart from each other. Therefore, the tubular packagingmaterial receives no pressure applied thereto.

As the seal portions are passed downward, and as the partial camfollowers engage the pressure surfaces, the pair of seal portion is nowpressed against each other. The tubular packaging material is sealedwhile the partial cam followers engage the pressure surfaces.

As the seal portions are passed further downward, the partial camfollowers now engage the exit surfaces. The pair of seal portionsseparates.

By disposing the entrance and exit surfaces above and below the pressuresurface, the partial cam followers can engage and disengage the partialcams smoothly. Therefore, the drive means does not need to output muchpower to move the seal portions.

Preferably, the latitudinal seal mechanism further comprises a pair offixed cams, cam followers, and driving means. The pair of fixed cams hasa shape corresponding to a locus of each of the pair of seal portions.The cam followers are adapted to support the seal portions and move suchthat the seal portions are engaged with the fixed cams. The drivingmeans moves the cam followers.

In this latitudinal seal mechanism, the heated pair of seal portionsmoves circularly, and seals the tubular packaging material by holdingthe tubular packaging material therebetween. A locus of the sealportions is designed to meet desired sealing conditions such as sealingtime. The latitudinal seal mechanism utilizes fixed cams having a shapethat corresponds to the locus of the seal portions, such that the sealportions move drawing the locus. Each seal portion is supported by a camfollower that moves along a fixed cam such that the cam follower remainsengaged with the fixed cam. In this manner, the seal portions movedrawing the predetermined locus, thereby sealing the tubular packagingmaterial.

In the aforementioned arrangement where the fixed cams and the camfollowers make the seal portions move so as to draw a predeterminedlocus, the partial cams and partial cam followers secure sealingpressure, as well as enable easy adjustment of sealing pressure.

Preferably, in the latitudinal seal mechanism, the cam follower supportsthe seal portion via an elastic member that extends when the partial camfollower engages the partial cam.

In this latitudinal seal mechanism, the seal portion moves along thefixed cam with the elastic member therebetween. When the partial camfollower engages the partial cam, the elastic member extends, such thatthe cam follower remains engaged with the fixed cam. Even if reactionaryforce occurs in the seal portions that press against each other, thereactionary force is transmitted to the partial cams via the partial camfollowers. Therefore, the reactionary force does not affect the elasticmembers, cam followers, or fixed cams.

More specifically, the latitudinal seal mechanism includes cam followersthat move so as to remain engaged with fixed cams. However, the camfollowers alone cannot make the seal portions contact each other; therealways remains a gap between the seal portions as long as the sealportions are supported only by the cam followers. The latitudinal sealmechanism also includes partial cam followers and partial cams. Thepartial cam followers and partial cams are disposed such that the sealportions are pressed against each other when the partial cam followersengage the partial cams. While the partial cam follower engage thepartial cams, the seal portions are supported by the partial cams,instead of the fixed cams.

Preferably, in the latitudinal seal mechanism, the driving means movesthe cam followers via a rotational shaft and a coupling member. Thedriving means member is adapted to rotate the rotational shaft. Therotational shaft is adapted to rotate the cam follower relativelycircularly about a rotational center of the rotational shaft. Thecoupling member connects the rotational shaft and the cam follower. Therotational shaft is adapted to move relative to the fixed cam in adirection that crosses with a direction of the length of the rotationalshaft, due to movement of the seal portion and the cam follower.

The cam followers are coupled to the rotational shafts. If therotational shafts are fixedly coupled, the cam followers cannot move butcircularly. However, in this latitudinal seal mechanism, the rotationalshafts can move in a direction that crosses with the direction of thelength thereof, for instance in a direction perpendicular to thedirection of the length thereof.

Preferably, in the latitudinal seal mechanism, the pair of seal portionsrubs the tubular packaging material through a movement of said camfollowers with a predetermined gap maintained between the pair of sealportions, before the partial cam followers engage the partial cams. Thepair of seal portions also seals the tubular packaging material byholding the tubular packaging material therebetween while the partialcam followers engage the partial cams.

In this latitudinal seal mechanism, the pair of seal portions rubs thetubular packaging material with a predetermined gap maintained betweenthe pair of seal portions, before the tubular packaging material issealed latitudinally. This rubbing is achieved by the cam followersmoving along the fixed cams. Since the tubular packaging material isrubbed before it is sealed, articles that are in the sealing portion ofthe tubular packaging material are pushed downward. Consequently,improper sealing that occurs due to articles sealed with the sealingportion of the tubular packaging can be avoided.

On the other hand, the tubular packaging material has to be pressedagainst each other to seal properly. This pressing operation is achievedby the partial cams and partial cam followers.

Preferably, in the latitudinal seal mechanism, a speed at which thedriving means moves the cam follower while the pair of seal portionsrubs the tubular packaging material is faster than a speed at which thedriving means moves the cam follower while the pair of seal portionsholds the tubular packaging material therebetween.

Since the speed at which the seal portions rub the tubular packagingportion is faster than the speed at which the tubular packaging materialis sealed, there is enough area in which the tubular packaging materialis rubbed.

In accordance with still another aspect of the present invention thereis a bag packaging mechanism that fills articles to be packaged whilesealing a tubular packaging material in longitudinal and latitudinaldirections. The bag packaging mechanism comprises forming means, apackaging material conveyance mechanism, a longitudinal seal mechanism,and a latitudinal seal mechanism. The forming means forms a sheet-shapedpackaging material supplied thereto in tubular shape while receiving thearticles to be packaged. The packaging material conveyance mechanismconveys the tubular packaging material in a downward direction. Thelongitudinal seal mechanism seals in a longitudinal directionoverlapping portions of the tubular packaging material conveyed thereto.The latitudinal seal mechanism is a latitudinal seal mechanism describedabove, and seals in a latitudinal direction portions of the tubularpackaging material conveyed thereto with a predetermined distancetherebetween.

These and other objects, features, aspects and advantages of the presentinvention will become more fully apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings where like reference numerals denote correspondingparts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the accompanying drawings which form a part of thisoriginal disclosure:

FIG. 1 is a perspective view of a bag packaging machine in accordancewith a first embodiment of the present invention;

FIG. 2 is a perspective view of a support frame of the bag packagingmachine depicted in FIG. 1 in accordance with the present inventionshown removed from the bag packaging machine;

FIG. 3 is a side view of a bag packaging unit of the bag packagingmachine depicted in FIG. 1 in accordance with the present invention;

FIG. 4 is a cross-sectional view of the bag packaging unit taken alongthe line IV—IV in FIG. 3, in accordance with the present invention;

FIG. 5 is a fragmentary view of the bag packaging unit depicted in FIG.4 as a slightly enlarged scale;

FIG. 6 is a cross-sectional view of a portion the bag packaging unittaken along the line VI—VI in FIG. 4 in accordance with the presentinvention;

FIG. 7 is a cross-sectional view of the bag packaging unit taken alongthe line VII—VII in FIG. 4 in accordance with the present invention;

FIG. 8 is a schematic view of a latitudinal seal pressure generationmechanism using partial cams for use with the bag packaging machine inaccordance with the present invention;

FIG. 9 is a schematic view of a heating control system for use in thebag packaging machine in accordance with present invention;

FIG. 10 is a view of the seal jaw being in a status where the camfollowers are on the arc surfaces of the fixed cams.

FIG. 11 is a view of seal jaws of the bag packaging machine shown withthe cam followers beginning to contact flat surfaces of the fixed cams;

FIG. 12 is a view of the seal jaws of the bag packaging machine with thecam followers in full contact with the flat surfaces of the fixed cams;

FIG. 13 is a view of the latitudinal seal pressure generation mechanismdepicted in FIG. 8 in accordance with the present invention.

FIG. 14 is a view showing rotational locuses of the seal jaws and thelocuses of the rotational shafts about the fixed cams;

FIG. 15 is a schematic view of conventional heating control system usedin the present invention;

FIG. 16 is a view of fixed cams in accordance with a second embodimentof the present invention; and

FIG. 17 is a schematic view of support mechanism that supports arotational shaft in accordance with the second embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment Overall Structure

FIGS. 1 and 3 show a bag packaging machine in accordance with the firstembodiment of the present invention. The bag packaging machine 1 showntherein is a machine for packaging, for instance, potato chips, andmainly includes a bag packaging unit 5 and a film supply unit (packagingmaterial supply unit) 6. The bag packaging unit 5 is a main portion ofthe bag packaging machine 1, in which potato chips are filled in bags.The film supply unit 6 supplies film to the bag packaging unit 5 suchthat the bags can be made from the film. On the front surface of the bagpackaging unit 5 are various operational switches 7. A LCD display 8that shows operational status of the bag packaging machine 1 is alsodisposed on a certain position such that an operator who operates theoperational switches 7 can visually recognize the display 8.

Structure of Each Unit

The film supply unit 6 supplies sheet-shaped film to a forming mechanism13 of the bag packaging unit 13. In the first embodiment, the filmsupply unit 6 is disposed adjacent to the bag packaging unit 5. The filmsupply unit 6 includes a roll of film, out of which film is supplied.Since replacement a roll requires a certain amount of space around thefilm supply unit 6, the film supply unit 6 does not need to be adjacentto the bag packaging unit 5. Instead, the film supply unit 6 and the bagpackaging unit 5 can be disposed apart from each other.

Referring to FIGS. 1 and 3, the bag packaging unit 5 includes a formingmechanism 13, a pull-down belt mechanism (packaging material conveyancemechanism) 14, a longitudinal seal mechanism 15, a latitudinal sealmechanism 17, and a support frame 12. The forming mechanism 13 forms thesheet-shaped films into a tubular shape. The pull-down belt mechanism 14conveys the film formed in the tubular shape (hereinafter referred to astubular film) in a downward direction. The longitudinal seal mechanism15 seals (heat-seals) overlapping portions of the tubular film in alongitudinal direction to form the tubular shape of the tubular film.The latitudinal seal mechanism 17 seals the tubular film in alatitudinal direction, thereby closing upper and bottom ends of thetubular film thereby forming sealed bags. The support frame 12 supportsthese mechanisms. A casing 9 is disposed around the support frame 12.

As shown in FIGS. 2 and 3, the support frame 12 includes four bottompillars 21, 22, 23 and 24, horizontal beams 25 a, 25 b, 25 c and 25 d,upper pillars 26 and 27, and a large pillar 28. The bottom pillars 21,22, 23 and 24 extend in a vertical upper direction from foot portions 21a, 22 a, 23 a and 24 a, which contact the floor of a factory. Thehorizontal beams 25 a, 25 b, 25 c and 25 d connect upper ends of thebottom pillars 21, 22, 23 and 24. The upper pillars 26 and 27 furtherextend in a vertical upper direction from the upper ends of the bottompillars 21 and 22. The large pillar 28 extends in a vertical upperdirection from a mid portion of the horizontal beam 25 c. Referring toFIG. 3, a ceiling plate 29 is fixedly coupled to upper portions of thelarge pillar 28 and the upper pillars 26 and 27. The ceiling plate 29has an opening in the center thereof. The support frame 12 supportsmechanisms 13, 14, 15, and 17 of the bag packaging unit 5. In thisembodiment, the support frame 12 also functions as a table that supportsa computerized scale 2.

As shown in FIG. 3, the forming mechanism 13 includes a tube 31 and aforming shoulder 32. The tube 31 is a tubular member with both upper andbottom ends open. The tube 31 is disposed on the center opening of theceiling plate 29 50 as to be integrated with the forming shoulder 32 viaa bracket. The bracket is not shown in figures. As each bag is formed,the bottom of the tubular film is sealed first. Then, potato chips arefilled in the opening of the upper end of the tube 31 by an amountcalculated by the computer scale 2. Thereafter, the top of the bag (andthe bottom of the next bag) is sealed by the latitudinal seal mechanism17. The forming shoulder 32 is disposed so as to surround the tube 31.The forming shoulder 32 is shaped such that sheet-shaped film F sentfrom the film supply unit 6 is formed in a tubular shape as it passesbetween the forming shoulder 32 and the tube 31. The forming shoulder 32is also supported by the support frame 12 via a support member not shownin figures. Additionally, as shown in FIGS. 1 and 3, the formingmechanism 13 is disposed in a space above the space surrounded by thefour bottom pillars 21, 22, 23 and 24. More specifically, the formingmechanism 13 is disposed in a space surrounded by the pillars 26, 27 and28. The tube 31 and forming shoulder 32 can be replaced so as to fit thesize of bags to be assembled and filled. When the tube 31 and/or formingshoulder 32 need to be replaced, an operator accesses the formingmechanism 13 between the large pillar 28 and the upper pillar 27, orbetween the large pillar 28 and the upper pillar 26. Therefore, theforming mechanism 13 is detachable with respect to the support frame 12.

The pull-down belt mechanism 14 and the longitudinal seal mechanism 15are supported by a rail 40 that hangs from the ceiling plate 29. Thepull-down belt mechanism 14 and the longitudinal seal mechanism 15 aredisposed so as to hold the tube 31 therebetween. When the tube 31 isreplaced, the mechanisms 14 and 15 are moved along the rail 40 untilthey come to the positions that are out of the way. The pull-down beltmechanism 14 directs the tubular film F that is wrapped around the tube31 in a downward direction with assistance of a vacuum source (notshown) that acts on the film 14 thereby holding the film F against thepull-down belt mechanism 14. The pull-down belt mechanism 14 mainlyincludes a drive roller 41, a driven roller, and a belt (contactportion) 43 which is configured to engage the film F in response tosuction from the vacuum source. The longitudinal seal mechanism 15pushes the overlapping portions of the tubular film F against the tube31 by a predetermined force while heating the portions, thereby sealingthe tubular film F in a longitudinal direction. The longitudinal sealmechanism 15 includes a heater and a heater belt (longitudinal sealportion) which is heated by a heater and contacts the overlappingportions of the tubular film F.

As shown in FIGS. 1 and 3, the pull-down belt mechanism 14 and thelongitudinal seal mechanism 15 are also disposed above a spacesurrounded by the four bottom pillars 21, 22, 23 and 24. Morespecifically, the pull-down belt mechanism 14 and the longitudinal sealmechanism 15 are in a space surrounded by the upper and large pillars26, 27 and 28.

Latitudinal Seal Mechanism

The latitudinal seal mechanism 17 will now be described below.

The latitudinal seal mechanism 17 is disposed below the formingmechanism 13, the pull-down mechanism 14, and the longitudinal sealmechanism 15. Referring to FIGS. 3 and 4, the latitudinal seal mechanism17 is supported by the bottom pillars 21, 22, 23 and 24 and thehorizontal beams 25 a, 25 b, 25 c and 25 d. As shown in FIG. 4, twosupport plates 72 are disposed in between the horizontal beam 25 c andthe horizontal beam 25 d. Four support members 74 are disposed betweenthe support plate 72 and the horizontal beam 25 a. Four support members73 are disposed between the other support plate 72 and the horizontalbeam 25 b.

The latitudinal seal mechanism 17 includes a pair of mechanisms 70 thatare symmetrically disposed between the beams 25 c and 25 d. FIG. 5 is anenlarged view of the mechanism 70 disposed closer to the horizontal beam25 d. Although following description pertains to the mechanism 70 on thehorizontal beam 25 d side, the mechanism 70 on the horizontal beam 25 cside has a generally identical mirror image structure.

The mechanism 70 is configured to rotate two seal jaws 78 about a cam(described below) such that the seal jaws 78 moves in a path having theshapes of the letter D. The mechanism 70 pushes the seal jaw 78 againstthe seal jaw 78 of the other mechanism 70 to seal the tubular film inthe latitudinal direction. As shown in FIGS. 5, 6 and 7, the mechanism70 includes fixed cams 75, cam followers 76, a rotational shaft 80,coupling members 79, seal jaws 78, partial cam followers 78 a, partialcams 88, and a motor 71.

The fixed cams 75 are disposed in a space between the two support plates72. The fixed cams 75 are fixed to the support plates 72. As shown inFIG. 6, the fixed cams 75 have a shape that is substantially the shapeof the letter D. Each of the fixed cams 75 has at its center anelongated bore 75 d that is elongated in the direction of the horizontalbeams 25 a and 25 b. Referring to FIG. 6, the fixed cam 75 includes aflat surface 75 a that faces the fixed cam 75 of the other mechanism 70.The upper and bottom surfaces of the fixed cam 75 form arc surfaces 75b. The surface opposite the flat surface 75 a forms a curved surface 75c.

Each fixed cam 75 engages two cam followers 76. The cam followers 76 arerotatably supported at opposite ends of the coupling member 79.Therefore, the distance between the two pairs of respective camfollowers 76 remains constant. Each cam follower 76 has two rollers 76 athat rotate while in contact with the peripheral surface of the fixedcam 75.

Referring to FIG. 5, the rotational shaft 80 extends through theopenings 72 a formed on the support plates 72 and the elongated bores 75d formed on the fixed cams 75. The rotational shaft 80 is pivotallysupported by the bearings 81 a which are disposed outside the spaceformed between the support plates 72. As shown in FIG. 5, the bearings81 a are fixed to the sliders 81. The sliders 81 slide along rails 82.Ends of respective ones of the rails 82 are fixed to respective supportmembers 73 or 74. In this manner, bearings 81 a move in the direction ofthe horizontal beams 25 a and 25 b. In other words, the rotational shaft80 is supported so as to be movable in the direction of the horizontalbeams 25 a and 25 b. The rotational shaft 80 extends through a portionof an elongated bore 75 d formed in a respective one of the fixed cams75 closest to the other mechanism 70 (hereinafter referred to as “innerside”) as shown in FIG. 10, and further the rotational shaft is movablewithin the elongated bore 75 d to a position farthest from the othermechanism 70 (hereinafter referred to as “outer side”) as shown in FIG.6. Additionally, the sliders 81 have ball bearings or cylinders thatroll on the rails 82. In this manner, the sliders 81 can slide againstthe rails 82 with little, if any, frictional resistance.

Referring to FIG. 5, the rotational shaft 80 engages a shaft 85 via aSchmidt coupling 84 therebetween. The shaft 85 engages a rotationalshaft 71 a of the motor 71 via a bevel gear 86. The Schmidt coupling 84is a shaft coupler having three disks that are linked together foraxially transmitting rotation of an input shaft, the shaft 85, to anoutput shaft, the rotational shaft 80. The Schmidt coupling 84 cantransmit rotation of the shaft 85 even when the rotational shaft 80moves relative to the shaft 85 in a direction perpendicular to therotational shaft 80, and therefore the distance between the two shaftschanges. Consequently, the rotational shaft 80 rotates as the motor 71rotates. The motor 71 is supported by the horizontal beams 25 a and 25d, while the rotational shaft 71 a of the motor 71 is supported bybearings fixed to the support members 74. The motor 71 is a servomotorthat is adapted to control rotational speed and/or torque.

The centers of the coupling members 79 are fixed to the rotational shaft80. Accordingly, the coupling members 79 rotate according to rotation ofthe rotational shaft 80. As described above, the cam followers 76 arecoupled to both ends of the coupling members 79. Accordingly, as shownin FIG. 6 and other figures, each pairs of cam followers 76 are disposedon opposite sides of the mechanism 70 with respect to the rotationalshaft 80. Changes in the distances between each pair of the camfollowers 76 and the rotational shaft 80 are the same during rotation.

Referring to FIGS. 5 and 6, the seal jaws 78 extend in the direction ofthe horizontal beams 25 c and 25 d. The seal jaws 78 are supported bythe cam followers 76 via plate springs 77 at two different positions.The plate spring 77 is capable of a few millimeters of compression. Aswill be described below, the plate springs 77 extend when the partialcam 88 engages the partial cam follower 78 a, and thereafter pulls thejaws 78 to restore the relative distance between the cam follower 76 andthe seal jaws 78. There are two partial cam followers 78 a on each sealjaw 78, one partial cam follower 78 a disposed at each opposite end ofthe two seal jaws 78, and are supported by the seal jaws 78. As shown inFIGS. 7 and 12, the partial cam followers 78 a rotate contacting aninner side surface of the partial cams 88 when the cam followers 76 passadjacent to the partial cams 88.

Each partial cam 88 is supported by the support plate 72 via a slider 89a and a rail 89 b as shown in FIGS. 8 and 13. One partial cam 88 isfixed to a corresponding slider 89 a, whereas the rail 89 b is fixed tothe support plate 72. The slider 89 a engages the rail 89 b, so as toslide along the rail 89 b in the direction of the horizontal beams 25 aand 25 b while being supported by the rail 89 b.

Referring to FIG. 8, the inner side surface of the partial cam 88includes an entrance surface 88 a, a pressure surface 88 b, and an exitsurface 88 c. As shown in FIG. 7, when the partial cam follower 78 aengages the entrance surface 88 a, opposing seal jaws 78 face each otherwith a gap therebetween as shown in FIGS. 4 and 6. The pressure surface88 b is formed immediately below the entrance surface 88 a. As shown inFIG. 12, when the partial cam follower 78 a engages the pressure surface88 b, the opposing seal jaws 78 are urged against each other. The exitsurface 88 c (FIG. 8) is formed immediately below the pressure surface88 b. When the partial cam follower 78 a engages the exit surface 88 c,the seal jaws 78 again face each other with a gap therebetween.

Referring to FIG. 8, the partial cam 88 and the partial cam 88 of theother mechanism 70 are coupled to each other via a link mechanism 98.The positions of the partial cams 88 are determined by an air cylinder96 that activates the link mechanism 98. As shown in FIG. 8, when theair cylinder 96 is connected with a high-pressure air supply, which isnot shown in figures, via an electromagnetic three-way valve 97, thepiston of the cylinder 96 is pulled up until it hits a stopper 99. Whenthe piston hits the stopper 99, the partial cams 88 are closest to eachother. At this point, the partial cam followers 78 a engage the pressuresurfaces 88 b, and the seal jaws 78 are forced against each other (FIG.12). The seal jaws 78 press against each other due to pressure from thepartial cams 88. In other words, the partial cams 88 receive reactionforce to move away from each other, from the seal jaws 78 via the camfollowers 78 a. However, the air cylinder 96 prevents the partial cams88 on both sides from moving away.

The latitudinal seal mechanism 17 includes therein a cutter device (notshown) that severs a bag from a following bag by cutting the middle ofthe portion sealed by the seal jaws 78.

Heat Control of Latitudinal Seal Mechanism

The latitudinal seal mechanism 17 crimps portions of tubular film in alatitudinal direction by holding tubular films between the seal jaws 78.To seal, the seal jaws 78 need to apply both pressure and heat. To heatcontacting surfaces (heated portion) of the seal jaws 78, which contactthe tubular film, each seal jaw 78 includes heaters 78 b (heating means)therein (FIG. 9). Also, each seal jaw 78 includes thermocouples 78 c tomonitor whether or not the temperature of the contacting surfaces of theseal jaws 78 is adequate.

A control unit 90 (FIG. 9) that rotates with the rotational shaft 80includes a controller 90 a. The controller 90 a monitors the temperatureby the thermo couples 78 c, and controls ON/OFF of the heaters 78 b. Asshown in FIG. 5, the control unit 90 is fixed to the support members 79a. The support members 79 a connect the coupling members 79 that arefixed to the rotational shaft 80. The control unit 90 includes, apartfrom the controller 90 a, memories 90 b and 90 c and switches 90 d and90 e (FIG. 9). The memories 90 b and 90 c store configured temperaturefor each heater 78 b. The switches 90 d and 90 e control ON/OFF of powersupply to each heater 78 b. Referring to FIGS. 5 and 9, power supplylines 91 a and compensating lead wires 91 b extend from the control unit90 to each of the seal jaws 78. The power supply lines 91 a supply powerto the heaters 78 b. The compensating lead wires 91 b connect the thermocouples 78 c and the controller 90 b.

Power is supplied to the controller 90 a and each heater 78 b from anexternal power source 93 through electricity distribution lines 92 thatinclude a slip ring 92 a. The slip ring 92 is utilized because theexternal power source 93 does not rotate. Power is first supplied thepower distribution lines 92 that are inside the rotational shaft 80,which does rotate. The power is supplied to the control unit 90, to bedistributed to the controller and each heater 78 b therefrom. As shownin FIG. 5, the slip ring 92 a is coupled to an end of the rotationalshaft 80 that is closer to the horizontal beam 25 b.

The controller 90 a controls power supply to each heater 78 b byswitching ON/OFF of the switches 90 d and 90 e. The heaters 78 b do notneed to be kept on at all times during operation of the bag packagingmachine 1. Instead, the heaters 78 b need to be on only enough to warm acontacting surface of a seal jaw 78 of which the temperature hasdecreased. Therefore, the controller 90 a of the control unit 90controls such that the sum of power supplied to each heater 78 b doesnot exceed a predetermined amount, by not turning the switches 90 d and90 e ON at the same time. In other words, the controller 90 a assignstime period to each heater 78 b, during which power is supplied to theheater 78 b.

Operation of Bag Packaging Machine

Operation of the bag packaging machine is explained below.

Sheet-shaped film F is sent from the film supply unit 6 to the formingmechanism 13, and then formed into a tubular shape as the film F passesthe forming shoulder 23 and is wrapped about the tube 31. Then, the filmF is conveyed in a downward direction by the pull-down belt mechanism14. The film F stays wrapped about the tube 31, with both endsoverlapping each other on the periphery of the tube 31. The longitudinalseal mechanism 15 seals the overlapping portions in a longitudinaldirection.

Once sealed, the tubular film F now has a tubular shape. The film Fpasses the tube 31, and is further sent down to the latitudinal sealmechanism 17. The position of the film F at this stage is depicted in atwo-dot chain line in FIG. 4. At this stage, as the tubular film Fmoves, a predetermined amount of potato chips are supplied from thecomputed scale 2 via the tube 31. At the latitudinal seal mechanism 17,the top and bottom ends of a bag are sealed in the latitudinal directionwith potato chips filled in the tubular film F.

Operation of Latitudinal Sealing of the Bag Packaging Machine

Operation of latitudinal sealing will now be explained.

In the latitudinal seal mechanism 17, rotation of the motor 71 moves thecam follower 76 and the seal jaw 78 in a circular manner about therotational shaft 80. Since the cam follower 76 is coupled to each end ofthe coupling member 79, the two cam followers 76 effectively hold thefixed cam 75 therebetween. Accordingly, the rollers 76 a of the camfollowers 76 move along the periphery of the fixed cam 75. Then, therotational shaft 80 moves horizontally as shown in FIGS. 6, 10, and 11.More specifically, when the rollers 76 a of the cam follower 76 are onthe arc surfaces 75 b as shown in FIG. 10, the rotational shaft 80 is onthe inner side of the elongated bore 75 d. As the latitudinal sealmechanism 17 shifts from a status shown in FIG. 11 to a status shown inFIG. 6, in other words, as rollers 76 a of one cam follower 76 move onthe flat surface 75 a and rollers 76 a of the other cam follower 76 moveon the curved surface 75 c, the rotational shaft 80 moves between theinner side and the outer side within the elongated bore 75 d. In thismanner, the rotational shaft 80 repeats stopping at the inner side ofthe elongated bore 75 d and moving linearly back and forth between theinner side and the outer side of the elongated bore 75 d. FIG. 14 showsa locus T2 of the rotational shaft 80.

The cam followers 76 rotate along the periphery of the fixed cam 75,drawing a locus in the shape of letter D, as described above. The sealjaws 78 also rotate following the cam followers 76. In addition, theseal jaws 78 rotate relative to the cam follower 76 when they are in thearea near the partial cam 88. As the inner cam follower 76 moves intothe flat surface 75 a, in other words from a status shown in FIG. 11 toa status shown in FIG. 6, a partial cam follower 78 a at an end of theseal jaw 78 engages an inner side surface (entrance surface 88 a) of thepartial cam 88, as shown in FIG. 7. Thereafter, the cam follower 76keeps moving while contacting the fixed cam 75. The seal jaw 78 movesdownward while moving horizontally away from the cam follower 76 (FIG.12). At this time, the plate spring 77 that couples the cam follower 76and the seal jaw 78 is extended. Accordingly, the seal jaw 78 and thecorresponding seal jaw 78 of the other mechanism push against eachother. Further, as the partial cam follower 78 a moves from the pressuresurface 88 b to the exit surface 88 c, the seal jaws 78 separate fromeach other. FIG. 14 shows rotational locuses T1 of the seal jaws 78,including the locus in the area near the partial cam 88. Specifically,the rotational locus T1 is a locus of an end of the seal jaw 78, inother words, a contacting surface of the seal jaw 78 that contacts thetubular film F.

In this manner, in the latitudinal seal mechanism 17, the seal jaw 78 ofone mechanism 70 rotates drawing a locus in the shape of letter D,whereas the seal jaw 78 of the other mechanism 70 rotates drawing alocus in the shape of inverted letter D. In the process of rotation, theseal jaws 78 of the two mechanisms 70 push against each other. (Seerotational locuses T1 of the seal jaws 78 in FIG. 14)

As a film F is passed down to the middle portion of the latitudinal sealmechanism 17, a portion of the tubular film F undergoes sliding contactwith the seal jaws 78 in the area of the latitudinal seal mechanism 17shown as “Sliding” in FIG. 14. In this process, the seal jaws 78 movedownward at a speed a few times faster than a conveyance speed of thetubular film F, with the contacting surfaces of the seal jaws 78 beingkept a few millimeters apart with the tubular film F therebetween. Inthis manner, potato chips C in the portion of the tubular film F to besealed are pushed downward such that potato chips C are not sealed withthe tubular film F at the time of sealing.

Next, as the seal jaws 78 move through the “Seal” area shown in FIG. 14,an upper portion of a bag B and a bottom portion of a following bag aresealed at the same time. At this process, the seal jaws 78 movebasically at the speed of conveyance of the tubular film F (now a bag).As the tubular film F is sealed, the cutter device disposed in the sealjaws 78 separates a bag B from the tubular film F.

In this manner, bags B are manufactured continuously, and delivered to abelt conveyer (not shown in figures) by an inclined delivery plate 19.The belt conveyer thereafter delivers the bags B to devices that conductother processes such as weight checkers.

Features of the Bag Packaging Machine

(1) In the bag packaging machine 1, the latitudinal seal mechanism 17 issupported by the support frame 12 on both sides, unlike a conventionalbag packaging machine which is supported in a cantilever manner. Thesupport frame 12 includes the foot portions 21 a, 22 a, 23 a and 24 athat are disposed so as to surround the latitudinal seal mechanism 17.The support frame 12 also includes four bottom pillars 21, 22, 23 and 24that extend in a vertical upper direction from the foot portions 21 a,22 a, 23 a and 24 a. Therefore, the support frame 12 can securelysupport the latitudinal seal mechanism 17. Accordingly, the latitudinalseal mechanism 17 does not rattle even when bag packaging process hasbeen conducted at a high speed. Notably, the latitudinal seal mechanism17 of the present embodiment rotates the seal jaws 78 in the shape ofletter D. Rotation of seal jaw generally leads to greater rattlingbecause of the weight and momentum of the seal jaw. However, since thelatitudinal seal mechanism 17 is supported on both ends in thisembodiment, the bag packaging machine of the present invention can keeprattling below an allowable level even at the time of high-speedprocessing.

Also, the latitudinal seal mechanism 17 is disposed within the supportframe 12, which includes four bottom pillars 21, 22, 23 and 24 andhorizontal beams 25 a, 25 b, 25 c and 25 that connect upper ends of thebottom pillars 21, 22, and 24. Therefore, the latitudinal seal mechanism17 is supported on front, back, left, and right sides. Accordingly, itis not likely that the latitudinal seal mechanism 17 will be displaceddue to rattling.

Although the latitudinal seal mechanism 17 is disposed within thesupport frame 12, with the seal jaws being within a space surrounded bythe four bottom pillars 21, 22, 23 and 24 in this embodiment, thelatitudinal seal mechanism 17 does not necessarily need to be within thesupport frame 12. The latitudinal seal mechanism 17 can be partiallyoutside the space surrounded by the four bottom pillars 21, 22, 23 and24, including the space thereabove.

(2) In the bag packaging machine 1 of the present embodiment, theforming mechanism 13, the pull-down belt mechanism 14, and thelongitudinal seal mechanism 15 are also supported by the support frame12 and disposed within a space above the space surrounded by the fourbottom pillars 21, 22, 23 and 24. The forming mechanism 13, the pulldown belt mechanism 14, and the longitudinal seal mechanism 15 form afilm in a tubular shape, deliver the film, and apply longitudinal sealprocess thereto in a continuous manner. Therefore, there is littlerattling due to the belt 43 of the pull down belt mechanism 14 and theheater belt of the longitudinal seal mechanism 15.

Further, as shown in FIGS. 1 and 3, the tube 31 of the forming mechanism13 is disposed such that the tube 31 is in the center of the supportframe 12 when viewed from above. Since the tube 31 is disposed above thespace surrounded by the foot portions 21 a, 22 a, 23 a and 24 a and thebottom pillars 21, 22, 23 and 24, the support frame 12 can also functionas a table for supporting the computer scale 2. Therefore, no additionaltable for supporting the computer scale 2 is required above the bagpackaging unit 5. Also, the bag packaging machine 1 and the computerscale 2 can be coordinated in an orderly manner.

(3) In the latitudinal seal mechanism 17 of the bag packaging machine 1of the present invention, the rotational shafts 80 slides against thefixed cams 75, unlike a conventional latitudinal seal mechanism wherethe cam followers 76 and the coupling members 79 slide against eachother. Therefore, the slide mechanism (the slider 81 and the rail 82)can be formed outside the space surrounded by the fixed cams 75, wherethere is more space. Accordingly, the latitudinal seal mechanism 17 ismore durable. In addition, the latitudinal seal mechanism 17 of thepresent embodiment has two cam followers 76 for each fixed cam 75. Ifthe latitudinal seal mechanism 17 had a structure where the camfollowers 76 slide against the coupling members 79, one mechanism 70would require four slide mechanisms. However, since the latitudinal sealmechanism 17 of the present embodiment has a structure where it is therotational shafts 80 that slides, there only need to be two slidemechanisms for each mechanism 70.

(4) The latitudinal seal mechanism 17 of the bag packaging machine 1 ofthe present embodiment has two cam followers 76 for each fixed cam 75.Therefore, the latitudinal seal mechanism 17 can seal latitudinallytwice per one rotation of the rotational shaft 80.

When viewed from side, the cam followers 76 are disposed so as to holdthe rotational shaft 80 therebetween, with the coupling member 79connecting all of them. This is why the latitudinal seal mechanism 17 ofthe present invention can utilize a plate cam that engages only innerside of the roller 76 a of the cam follower 76, instead of a groove camthat engages both inner and outer sides of the rollers 76 a of the camfollower 76. In other words, since the cam followers 76 hold the fixedcam 75 therebetween, the cam followers 76 do not disengage the fixed cam75, even if the fixed cam 75 is a plate cam.

(5) In the latitudinal seal mechanism 17 of the bag packaging machine ofthe present invention, partial cam followers 78 a are disposed on bothends of the seal jaws 78. The latitudinal seal mechanism 17 alsoincludes a pair of partial cams 88 that engages the seal jaws 78 and thetubular film F when the tubular film F is held between the opposing sealjaws 78. The latitudinal seal mechanism 17 also includes a linkmechanism 98 and an air cylinder 96 (See FIG. 8) that apply force to thepair of partial cams 88. In this manner, the seal jaws 78 are pressedagainst each other only at the time of sealing. Also, the pressing forceis generated by the air cylinder 96, instead of the motor 71. Therefore,there is no need for a motor that generates torque that is large enoughto oppose the sealing pressure, whereby cost is reduced.

Also in this embodiment, the force by which the seal jaws 78 hold aportion of the tubular film F to be sealed, in other words the sealingpressure, can be controlled by adjusting the electromagnetic three-wayvalve 97, which controls the pressure inside the air cylinder 96.

Additionally, the air cylinder 96 applies force in a perpendiculardirection (vertical direction) relative to the direction of sealpressure (horizontal direction) through the link mechanism 98. The linkmechanism 98 also connects the partial cams 99. Therefore, a greaterseal pressure can be generated with a small air pressure.

Furthermore, by disconnecting the connection between the high pressureair supply and the air cylinder through operation of the electromagneticthree-way valve 97, the gap between the partial cams 88 is enlarged fromS1 (FIG. 8) to S2 (FIG. 13). In this manner, if bags should not besealed latitudinally, for instance when the quality of potato chips isnot ensured, low quality potato chips can be thrown away before sealingthe bags.

Although the present embodiment utilizes the air cylinder 96, othermeans such as an oil pressure cylinder can also be utilized.

(6) The partial cam 88 of the latitudinal seal mechanism 17 of the bagpackaging machine 1 includes on an inner side thereof an entrancesurface 88 a, a pressure surface 88 b, and an exit surface 88 c, whichare formed continuously. Accordingly, the locus that the seal jaw 78draws as it moves while the partial cam follower 78 a engages thepartial cam 88 is smooth, consequently, less power is required from themotor 71 to rotate the seal jaw 78. Additionally, since the pressuresurface 88 b of this embodiment includes the entrance surface 88 a andthe exit surface 88 c at the top and bottom thereof, the cam follower 78a can can smoothly engage and disengage the partial cam 88, withoutdisrupting rotation of the partial cam follower 78 a (See FIG. 14).Accordingly, even less power is required from the motor 71.

(7) In a conventional latitudinal seal mechanism, an external controlunit 190 is disposed apart from a structure that rotates about therotational shaft 180, as shown in FIG. 15. Accordingly, there has to bea slip ring 192 on distribution lines that connects the external controlunit 190 and devices inside the seal jaw 178 of the latitudinal sealmechanism, such as the heaters 178 b and the thermometers 178 c. Whenmore than one seal jaws 178 are disposed on one rotational shaft 180 asshown in FIG. 15, the number of poles of the slip rings 192 a has to beincreased accordingly. For instance, if there are two seal jaws 178 asshown in FIG. 15, four power lines for supplying power to each heater178 b and four signal lines to retrieve signal from each thermometer 178c are needed. In other words, there have to be eight poles of slip rings192 a.

On the other hand, the latitudinal seal mechanism 17 of the bagpackaging mechanism 1 of the present invention shown in FIG. 9 has astructure in which the control unit 90 rotates together with therotational shaft 80. Therefore, there is no relative rotation betweenthe control unit 90 and devices that rotate with the rotational shaft80, such as the heater 78 b and the thermo couples 78 c that control theheater 78 b. Accordingly, no slip ring is needed on the distributionlines that lie between the heater 78 b and the control unit 90, andbetween the thermo couples 78 c and the control unit 90. The only slipring needed is the slip ring 92 a for supplying power from the externalpower source 93 to the control unit 90. Reducing the number of poles ofthe slip ring 92 a reduces the overall cost. Further, by not disposing aslip ring on compensating lead wires, noises can be prevented. Thereforemore reliable control is assured.

(8) The latitudinal seal mechanism 17 of the bag packaging mechanism 1assigns to each heater 78 b a time period in which the heater 78 b issupplied with power. Therefore, only two poles of the slip ring 92 a onthe power supply lines 92 suffice. Also, the slip ring 92 a only needslimited capacity.

Second Embodiment

In the first embodiment, the rotational shafts 80 are supported by thebearings 81 a fixed to the sliders 81 which are adapted to slide alongthe rails 82, such that the rotational shafts 80 are movable in thedirection of the horizontal beams 25 a and 25 b. However, as shown inFIG. 17, the rotational shafts 80 can also be supported such that therotational shafts 80 can move rotationally drawing an arc.

In the example shown in FIG. 17, the rotational shaft 80 is pivotablysupported by a bearing 181 a. The bearing 181 a has an arm 181 b fixedthereto. A pin 181 c is fixed to a bottom end of the arm 181 b. The pin181 c is pivotably supported by another bearing 182, which is supportedby the support frame 12. In other words, the rotational shaft 80 isrotatable about the pin 181 c, while being rotatably supported by thebearing 181 a.

The rotational shaft 80 supported in the aforementioned manner can movein the direction of the horizontal beams 25 a and 25 b drawing anarc-shaped locus T3, as the two cam followers 76 rotate. The two camfollowers 76 are coupled to a fixed cam 175, such as the one shown inFIG. 16. The coupling member 79 connects the cam followers 79 and therotational shaft 180, such that the rotational shaft 180 moves followingrotation of the cam followers 67. More specifically, the rotationalshaft 180 repeats stopping at the inner position and arc-shaped back andforth movement.

This arrangement can also eliminate a structure in which the camfollowers 76 and the coupling member 79 slide against each other, bymoving the rotational shaft 80. Consequently, the sliding portionbecomes more durable.

Third Embodiment

In the first embodiment, two cam followers 76 are disposed for eachfixed cam 75. If only one cam follower 76 is to be disposed for eachfixed cam 75, the fixed cam 75 can be a groove cam with the cam follower76 engaging the groove. Alternatively, the second cam follower without aseal jaw can be disposed such that the two cam followers oppose eachother across the rotational shaft 80.

Although the first embodiment discloses a fixed cam 75 having two camfollowers 76, a fixed cam 75 can have three or more cam followers 76 tofurther increase the speed of processing.

Fourth Embodiment

In the first embodiment, the present invention has been applied to alatitudinal seal mechanism where the fixed cams 75 and the cam followers76 through the motor 71 let the seal jaws 78 draw a locus in the shapeof letter D. The present invention can also be applied to a latitudinalseal mechanism where two kinds of motors (rotational motor andhorizontal motor) move seal jaws so as to draw a locus of letter D, asdisclosed in Japanese Laid-Open Patent Application 10-86910.

In that case, sealing pressure can be generated by the partial cams andthe partial cam followers, and by the link mechanism and the aircylinder. Therefore, the horizontal motor does not need to be able togenerate torque that is comparable to the sealing pressure. Therefore, amotor with small torque capacity can function as the horizontal motor.

Referring to FIG. 8, by making the entrance surfaces 88 a inclined bysmall angle relative to the vertical direction, even a low-poweredrotational motor can rotate the seal jaws and partial cam followers,pushing the seal jaws and partial cam followers against the sealingpressure.

In this manner, when the present invention is applied to a latitudinalseal mechanism disclosed in Japanese Laid-Open patent application10-86910, the rotational motor and horizontal motor can be reduced insize. Therefore, cost of bag packaging machine can be reducedaccordingly.

Fifth Embodiment

In the first embodiment, the rotational shafts 80 move relative to thefixed cams 75. The seal jaws 78 can move so as to draw a locus in theshape of letter D, by eliminating relative movement between the fixedcams 75 and the rotational shafts 80, and instead having the couplingmembers 79 and the cam followers 76 slide against each other. Thisembodiment also has the aforementioned effects of the present invention.

Effect of Invention

This invention generates sealing pressure without causing much burden todriving means that moves the seal portion circularly, by use of a pairof partial cams and partial cam followers that engage each partial cams.In other words, in the present invention, sealing pressure can be easilysecured in the latitudinal seal mechanism by use of partial cams andpartial cam followers.

Also, according to another aspect of the present invention, sincemagnitude of pressure applied to the partial cams by the pressure meansvia the pressure adjustment means is adjustable, the magnitude ofsealing pressure can be adjusted, or it can be adjusted that thelatitudinal seal mechanism does not seal at all.

Since the rotational shaft moves relative to the fixed cam in thisinvention, there is more flexibility as to where the sliding structure(shaft support portion) can be disposed. Additionally, the presentinvention eliminates the structure in which the coupling member fixed tothe rotational shaft and the cam follower slide against each other.

While several embodiments have been chosen to illustrate the presentinvention, it will be apparent to those skilled in the art from thisdisclosure that various changes and modifications can be made hereinwithout departing from the scope of the invention as defined in theappended claims. Furthermore, the foregoing description of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A latitudinal seal mechanism for use in a bagpackaging mechanism that fills articles to be packaged while sealing atubular packaging material in longitudinal and latitudinal directions,said latitudinal sealing mechanism comprising: a pair of fixed camsfixedly supported in the bag packaging mechanism; a pair of seal memberscoupled to said pair of fixed cams, each of said seal members beingarranged and configured to move about one of said fixed cams in agenerally circular path; first and second partial cam followerssupported on said seal members; first and second partial cams havingfirst and second surfaces that are selectively engageable with saidfirst and second partial cam followers, respectively, for selectivelymoving said seal members toward one another, such that said seal membersengage and hold a portion of the tubular packaging material between saidseal members as said seal members approach one another; and a linkmechanism that connects said first partial cam to said second partialcam.
 2. The latitudinal seal mechanism as set forth in claim 1, furthercomprising pressure means for applying pressure to said first and secondpartial cams such that said seal members press against each other withsaid seal members holding the tubular packaging material therebetween.3. The latitudinal seal mechanism as set forth in claim 2, furthercomprising pressure adjustment means for adjusting a magnitude ofpressure that said pressure means applies to said first and secondpartial cams.
 4. A latitudinal seal mechanism for use in a bag packagingmechanism that fills articles to be packaged while sealing a tubularpackaging material in longitudinal and latitudinal directions, saidlatitudinal sealing mechanism comprising: a pair of fixed cams fixedlysupported in the bag packaging mechanism; a pair of seal members coupledto said pair of fixed cams, each of said of seal members being arrangedand configured to move about one of said fixed cams in a generallycircular path; first and second partial cam followers supported on saidseal members; first and second partial cams having first and secondsurfaces that are selectively engageable with said first and secondpartial cam followers, respectively, for selectively moving said sealmembers toward one another, such that said seal members engage and holda portion of the tubular packaging material between said seal members assaid seal members approach one another, said first and second partialcams being connected via a link mechanism; pressure means for applyingpressure to said first and second partial cams such that said sealmembers press against each other with said seal members holding thetubular packaging material therebetween, said pressure means applyingforce to a portion of said link mechanism in a direction perpendicularto a direction in which said seal members move to press against eachother; and pressure adjustment means for adjusting a magnitude ofpressure that said pressure means applies to said first and secondpartial cams.
 5. The latitudinal seal mechanism as set forth in claim 4,wherein said first and second partial cams include respective opposingsurfaces, each of said opposing surfaces has an entrance surface, apressure surface, and an exit surface, said pressure surface beingformed immediately below said entrance surface, said exit surface beingformed immediately below said pressure surface, said seal membersreceiving no pressure applied thereto while said first and secondpartial cam followers engage said entrance surfaces, said seal membersbeing pressed against each other while said first and second partial camfollowers engage said pressure surfaces, said seal members receiving nopressure applied thereto while said first and second partial camfollowers engage said exit surfaces.
 6. A latitudinal seal mechanism foruse in a bag packaging mechanism that fills articles to be packagedwhile sealing a tubular packaging material in longitudinal andlatitudinal directions, said latitudinal sealing mechanism comprising: apair of fixed cams fixedly supported in the bag packaging mechanism; apair of seal members coupled to said pair of fixed cams, each of saidseal members being arranged and configured to move about one of saidfixed cams in a generally circular path, each of said fixed cams havinga shape corresponding to one of the circular paths followed by said sealmembers; partial cam followers supported on respective ones of said sealmembers; a pair of partial cams having surfaces that are selectivelyengageable with said partial cam followers for selectively moving saidseal members toward one another, such that said seal members engage andhold a portion of the tubular packaging material between said sealmembers as said seal members approach one another; said pair of partialcams being connected to each other via a link mechanism; said pair ofpartial cams including respective opposing surfaces, each of saidopposing surfaces having an entrance surface, a pressure surface, and anexit surface, said pressure surface being formed immediately below saidentrance surface, said exit surface being formed immediately below saidpressure surface, said seal members receiving no pressure appliedthereto while said partial cam followers engage said entrance surfaces,said seal members being pressed against each other while said partialcam followers engage said pressure surfaces, said seal members receivingno pressure applied thereto while said partial cam followers engage saidexit surfaces; pressure means for applying pressure to said partial camssuch that said seal members press against each other with said sealmembers holding the tubular packaging material therebetween, saidpressure means applying force to a portion of said link mechanism in adirection perpendicular to a direction in which said seal members moveto press against each other; pressure adjustment means for adjusting amagnitude of pressure that said pressure means applies to said partialcams; cam followers coupled between said seal members and said fixedcams, such that said seal members are engageable with said fixed cams;and driving means for moving said cam followers.
 7. The latitudinal sealmechanism as set forth in claim 6, wherein each of said cam followerssupports one of said seal members via an elastic member that isextendable in response to said partial cam follower supported on saidone of said seal members engaging one of said partial cams.
 8. Thelatitudinal seal mechanism as set forth in claim 7, wherein said drivingmeans moves said cam followers via at least one rotational shaft and atleast one coupling member, said driving means rotating said rotationalshaft, said rotational shaft rotating said cam followers relativelycircularly about a rotational center of said rotational shaft, saidcoupling member connecting said rotational shaft and said cam followers;and said rotational shaft being arranged and configured to move relativeto one of said fixed cams in a direction perpendicular to a length ofsaid rotational shaft, due to movement of said seal members and said camfollowers.
 9. The latitudinal seal mechanism as set forth in claim 8,wherein said seal members slide along a portion of the tubular packagingmaterial in response to movement of said cam followers with apredetermined gap maintained between said seal members prior to saidpartial cam followers engaging said partial cams, and said seal memberssealing the tubular packaging material by holding the tubular packagingmaterial therebetween while said partial cam followers engage saidpartial cams.
 10. The latitudinal seal mechanism as set forth in claim9, wherein a speed at which said driving means moves said cam followerswhile said seal members slide on the tubular packaging material isfaster than a speed at which said driving means moves said cam followersas said seal members hold the tubular packaging material therebetween.11. A bag packaging mechanism that fills articles to be packaged whilesealing a tubular packaging material in longitudinal and latitudinaldirections, said bag packaging mechanism comprising: forming means forforming a sheet-shaped packaging material supplied thereto in a tubularshape while receiving the articles to be packaged; a packaging materialconveyance mechanism for conveying the tubular packaging material in adownward direction; a longitudinal seal mechanism for sealing in alongitudinal direction overlapping portions of the tubular packagingmaterial conveyed thereto; and a latitudinal seal mechanism for sealingin a latitudinal direction portions of the tubular packaging materialconveyed thereto with a predetermined distance therebetween, saidlatitudinal seal mechanism comprising: a pair of fixed cams fixedlysupported in the bag packaging mechanism; a pair of seal members coupledto said pair of fixed cams, each of said seal members being arranged andconfigured to move about one of said fixed cams in a generally circularpath; partial cam followers supported on respective ones of said sealmembers; a pair of partial cams having surfaces that are selectivelyengageable with said partial cam followers for selectively moving saidseal members toward one another, such that said seal members engage andhold a portion of the tubular packaging material between said sealmembers as said seal members approach one another; and a link mechanismthat connects said pair of partial cams together.